But how do you know when behaviour crosses boundaries, when the balance goes too far and you’re making compromises where you shouldn’t be or accepting behaviour that is actually toxic? Sometimes it can be hard to see things objectively when you’re blinded by love or simply feel stuck.

One form of behaviour that often falls into this camp is gaslighting.

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What is gaslighting?

Gaslighting might be an unfamiliar word, but the experience will resonate with many people who have experienced controlling relationships. It describes a situation where one party psychologically manipulates the other, making them doubt their own version of events, or even their own sanity.

For example, if you believe that your partner might be being unfaithful so you call them out on it, and instead of having a conversation about your concerns, they call you crazy or other derogatory names.

And that term? It comes from ‘Gas Light’, a 1938 play about a married couple, in which an abusive husband makes his wife believe she has gone mad.

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What does gaslighting look and feel like?

Katie Ghose, chief executive of Women’s Aid, said: “From our work with survivors, we know that perpetrators of domestic abuse will use every tactic available to them to try to exert power and control over survivors.

Ghose said the gaslighting techniques abusers use include calling into question your memory of an incident, trivialising your thoughts or feelings, accusing you of lying or making things up, denying things like promises that have been made, and mocking you for “misconceptions”.

“This form of abuse can be subtle therefore some of the signs to watch out for include: if you are second-guessing yourself all the time, feel confused, find yourself always apologising to your partner, you are having trouble making simple decisions and find yourself withholding information from friends and family so you don’t have to explain or make excuses for your partner.”

When does this happen?

But the term has grown in usage in recent years, gaining traction when Women’s Aid used it publicly to call out the behaviour of Love Island’s Adam Collard, towards fellow contestant Rosie Williams in 2018.

The pair were involved in a heated argument with Williams accusing Collard of ignoring her in favour of new contestant Zara McDermott. Collard, in turn, said Williams was overreacting, and her jealousy had “pushed him away”. Ghose, said Collard’s behaviour exhibited signs of “gaslighting and emotional abuse”.

Why is gaslighting problematic?

Everyone’s relationship is different and some people might believe this is just how they interact with their partner. But gaslighting should be taken seriously – it is a form of abuse, according to Martin Burrow, senior practice consultant at relationship support charity, Relate.

Burrow tells HuffPost UK: “It’s a form of abuse which can involve manipulation and undermining a person’s self-belief, sometimes to the point where they question their own sanity. Gaslighting can be used as a way of controlling a partner, something which is never acceptable.”